In the sampling or treatment of body tissues, and particularly brain tissue, it is important to be able to identify areas of tissue which require such sampling or treatment and to guide a cannula or biopsy needle to such areas. Once the needle or cannula is properly in place, a biopsy sample can be removed or a particular agent can be injected to such area through the cannula.
The precise placement of the needle in the target area is a critical step for obtaining biopsy samples. To locate the target area, a surgeon must first locate the general area within the skull in which the target area is located. This has typically been done using X-ray photography, although most recently, the use of CT (computerized tomography) scanning and NMR (nuclear magnetic resonance) have become more commonly used. However, CT scanners and, to a much greater extent, NMR machines, are considerably more expensive and less available than ultrasound and X-ray equipment, and require greater amounts of dedicated space.
The most common technique currently in use by neurosurgeons for locating lesions in the brain comprises fitting a circular crown containing precisely located pieces of radioactive material to the head of an individual and taking X-rays of the patient's head from various angles. Thereafter, the X-rays are examined using various trigonometric functions and the location of the lesions to be biopsied is determined. Similar techniques are utilized for CT scan detection of lesions.
Once the lesion is precisely located, the surgeon must then drill through the skull in the general area in which the lesion is located and take a biopsy of the tissue in that area. To take the biopsy, a biopsy needle is guided to the target area by means of a biopsy needle guide. Various such guides have been described in the prior art.
U.S. Pat. No. 3,021,842 issued to Flood discloses a device including a mounting plate that mounts to the surface of the skull or other bone tissue, and a spherical guide and a pair of locking rings for securing the spherical guide in said mounting plate. The spherical guide has a hole extending therethrough which can accommodate a needle.
U.S. Pat. No. 3,017,887 issued to Heyer discloses a brain surgery instrument for use in injecting various agents into the brain comprising a base that clamps to the skull, a ball disposed within a retaining ring in the base and a tube disposed through the ball from outside the skull to inside the brain. The tube can pivot but only a minimal amount. A protractor is provided to define the angle of the tube with respect to the skull.
U.S. Pat. Nos. 3,135,263 and 3,460,537 describe similar surgical instrument guides for use in positioning needles and the like in the brain.
All of the foregoing devices are designed to be used after the precise target area is identified using X-ray photography to identify the exact position of the lesion or other target area, and none can be used with ultrasound imaging to quickly, conveniently and precisely identify the target area and guide a biopsy needle or other instrument to the target area. Moreover, most of the foregoing devices have a very limited range of motion. Further, the devices generally require the taking of X-ray photographs while the biopsy or other instrumentation is disposed within the brain to be certain that the target area is reached by such instrumentation before the biopsy sample is obtained or any other treatment is performed on the brain tissue. The foregoing limitations of the prior art devices are overcome by the present invention, and other new and novel features of the present invention are described herein.